1. Field of the Invention
The present invention relates to a three-dimensional molding technique, and more particularly to a three-dimensional molding technique for generating a three-dimensional molded article by allowing a powder material to bind by applying a binder.
2. Description of the Background Art
As conventional three-dimensional molding apparatuses, there is known an apparatus whereby a binder which will harden when dried is discharged to a layer of powder material by means of inkjet and the like, and a bound body of the powder material is sequentially formed to mold a three-dimensional molded article. In such a three-dimensional molding apparatus, the operations as will be described below will be carried out for generating a three-dimensional molded article, for example.
At first a powder material of gypsum or starch is uniformly spread in a thin layer by means of a roller mechanism or the like. Next, a region where the powder material is to be molded in this thin layer is scanned by an inkjet head and then a binder which will harden when dried is applied. The powder material in the region where the binder was applied binds to a lower layer or a hardening region adjacent thereto. The process of sequentially forming a thin layer of powder material and applying a binder is repeated until molding is completed. Once molding has completed, the powder material in regions where the binder is not applied keep the condition that particles of powder are independent of each other, the three-dimensional molded article that has been bound by the binder can be taken out.
However, in the three-dimensional molding apparatus mentioned above, since a binder which will harden when dried is used, a time for drying the binder to bind the powder material after application of the binder is required, which hinders speed up of molding.
In addition, in the case of applying the above-mentioned binder using an inkjet head, the hole diameter of the nozzle portion is small (not more than 20 μm), so that when a binder having a strong adhesive strength is used, the binder will easily harden due to drying and likely to cause blocking. If such a malfunction occurs, the powder material in the region where the binder is to be applied will not be bound by the blocked nozzle, which will lead deterioration of shape accuracy and strength of a resultant three-dimensional molded article.
For this reason, in the case where an inkjet head is used, only a binder of weak adhesive strength can be used, and the strength of a finished three-dimensional molded article becomes low. In addition, in such a case, only a powder material which will bind by means of a binder having a weak adhesive strength can be used, so that the flexibility in selecting the powder material is limited.